Hi @batmat,
The LCD module that you are referring to as the one based on the GPIO bus is the Enhanced LCD Interface (eLCDIF) module, which is designed specifically for driving displays.
The other module would be the Smart External Memory Controller (SEMC) module which can definitely be used to drive certain types of displays, but its design is more specifically for driving of external memories, although most 8080-based displays also fit the SEMC capabilities when this module is combined with the capabilities of the FlexIO pins. The following application describes this functionality: https://mcuxpresso.nxp.com/appcodehub?search=an-flexio_8080_rt1050
From a quick look at the ILI9341 datasheet, I believe this driver supports several types of interfaces, including the RGB interface that is compatible with the eLCDIF module, the 8080 interface which is compatible with the SEMC module, and even 3/4-line SPI interface, that could be implemented using the LPSPI module.
That said, the best recommendation would be whatever fits your performance requirements, and available pinouts.
With respect to the SEMC signals, the WRX (write signal) and RDX (read signal) are both defined on specific FlexIO pins. In the case of the aforementioned Application Note, these would be FlexIO2_00 and FlexIO2_01 respectively. The D/CX signal is equivalent to the Register Select (RS) signal to determine if the data lines will send data or command information.
BR,
Edwin.